
\begin{tikzpicture}[ultra thick]
\ifx\du\undefined
  \newlength{\du}
  \fi
  \setlength{\du}{2\unitlength}
% \ifx\du\undefined
%   \newlength{\du}
%   \fi
%   \setlength{\du}{2.5\unitlength}
% \draw[help lines,step=5\du] (-55\du,0\du) grid (40\du,70\du);
\draw(-55\du,0\du)--(-35\du,0\du);
\draw(-20\du,0\du)--(-10\du,0\du);
\draw(-10\du,0\du)--(-5\du,15\du);
\draw(-20\du,0\du)--(-15\du,15\du);
\draw(-15\du,15\du)--(-11\du,21.5\du);
\draw(-11\du,21.5\du)--(-15\du,25\du);
\draw(-35\du,0\du)--(-15\du,25\du);
% \draw(-55\du,0\du)--(-20\du,45\du);
\draw(-55\du,0\du)--(-35\du,25\du)--(-25\du,45\du)--(-20\du,50\du)--(-20\du,65\du);
% \draw(-10\du,50\du)--(-10\du,45\du);
\draw(0\du,22.5\du)--(-10\du,32.5\du);
\draw(-5\du,45\du)--(-10\du,32.5\du);
\draw(40\du,0\du)--(30\du,0\du);
\draw(15\du,0\du)--(0\du,0\du);
\draw(0\du,0\du)--(-5\du,15\du);
\draw(15\du,0\du)--(10\du,15\du);
\draw(10\du,20\du)--(10\du,15\du);
\draw(10\du,20\du)--(14\du,30\du);
\draw(30\du,0\du)--(14\du,30\du);
% \draw(45\du,0\du)--(10\du,45\du);
\draw(40\du,0\du)--(25\du,30\du)--(5\du,50\du)--(5\du,65\du);
% \draw(10\du,50\du)--(10\du,45\du);
\draw(0\du,22.5\du)--(5\du,35\du);
\draw(-5\du,45\du)--(5\du,35\du);
% \pgfmathsetmacro{\Xb}{random(7)};
\draw[thick](-40\du,0\du)--(-39\du,1\du)--(-39\du,2\du)--(-39\du,3\du)--(-38\du,4\du)--(-40\du,5\du)--(-40\du,6\du)--(-39\du,7\du)--(-39\du,8\du)--(-39\du,9\du)--(-39\du,10\du);
\fill(-39\du,10\du)[black]circle(2.5pt);
\fill(-15\du,50\du)[black]circle(2.5pt);
\fill(-5\du,60\du)[black]circle(2.5pt);
\fill(10\du,40\du)[black]circle(2.5pt);
\node at (-45\du,-5\du)[below]{\bf A};
\node at (-15\du,-5\du)[below]{\bf B};
\node at (7.5\du,-5\du)[below]{\bf C};
\node at (35\du,-5\du)[below]{\bf D};
\node at (-50\du,-7\du)[above]{\small a$_1$};
\node at (-45\du,-7\du)[above]{\small a$_2$};
\node at (-40\du,-7\du)[above]{\small a$_3$};
\node at (-15\du,-7\du)[above]{\small b$_1$};
\node at (5\du,-7\du)[above]{\small c$_1$};
\node at (10\du,-7\du)[above]{\small c$_2$};
\node at (35\du,-7\du)[above]{\small d$_1$};
% \draw[thick](-39\du,10\du)--(-15\du,50\du);
% \draw[thick](-15\du,50\du)--(-5\du,60\du);
% \draw[thick](10\du,40\du)--(-5\du,60\du);
% \draw[thick](35\du,0\du)--(20\du,30\du);
% \draw[thick](20\du,30\du)--(10\du,40\du);
% \draw[thick](-15\du,0\du)--(-10\du,15\du);
% \draw[thick](-10\du,15\du)--(0\du,20\du);
% \draw[thick](0\du,20\du)--(10\du,40\du);
% \draw[thick](5\du,0\du)--(0\du,15\du);
% \draw[thick](10\du,0\du)--(5\du,15\du);
% \draw[thick](0\du,15\du)--(-15\du,30\du);
% \draw[thick](-15\du,30\du)--(-15\du,50\du);
% \draw[thick](5\du,15\du)--(10\du,40\du);
\draw[thick](-39\du,10\du)--(-38\du,12\du)--(-36\du,14\du)--(-36\du,16\du)--(-35\du,18\du)--(-32\du,20\du)--(-32\du,22\du)--(-31\du,24\du)--(-30\du,26\du)--(-29\du,28\du)--(-28\du,30\du)--(-25\du,32\du)--(-24\du,34\du)--(-23\du,36\du)--(-23\du,38\du)--(-22\du,40\du)--(-20\du,42\du)--(-18\du,44\du)--(-18\du,46\du)--(-17\du,48\du)--(-15\du,50\du);
\draw[thick](-15\du,50\du)--(-15\du,51\du)--(-13\du,52\du)--(-12\du,53\du)--(-11\du,54\du)--(-10\du,55\du)--(-9\du,56\du)--(-8\du,57\du)--(-7\du,58\du)--(-7\du,59\du)--(-5\du,60\du);
\draw[thick](10\du,40\du)--(9\du,42\du)--(6\du,44\du)--(5\du,46\du)--(4\du,48\du)--(3\du,50\du)--(0\du,52\du)--(0\du,54\du)--(-1\du,56\du)--(-4\du,58\du)--(-5\du,60\du);
\draw[thick](35\du,0\du)--(34\du,2\du)--(33\du,4\du)--(32\du,6\du)--(31\du,8\du)--(30\du,10\du)--(30\du,12\du)--(29\du,14\du)--(27\du,16\du)--(26\du,18\du)--(26\du,20\du)--(24\du,22\du)--(23\du,24\du)--(23\du,26\du)--(22\du,28\du)--(20\du,30\du);
\draw[thick](20\du,30\du)--(19\du,31\du)--(18\du,32\du)--(17\du,33\du)--(15\du,34\du)--(15\du,35\du)--(14\du,36\du)--(12\du,37\du)--(13\du,38\du)--(10\du,39\du)--(10\du,40\du);
\draw[thick](-15\du,0\du)--(-15\du,1\du)--(-15\du,3\du)--(-14\du,4\du)--(-14\du,5\du)--(-13\du,7\du)--(-11\du,9\du)--(-11\du,10\du)--(-11\du,11\du)--(-12\du,12\du)--(-11\du,13\du)--(-11\du,14\du)--(-10\du,15\du);
\draw[thick](-10\du,15\du)--(-8\du,16\du)--(-6\du,17\du)--(-4\du,18\du)--(-2\du,19\du)--(0\du,20\du);
\draw[thick](0\du,20\du)--(2\du,24\du)--(3\du,26\du)--(4\du,28\du)--(5\du,30\du)--(6\du,32\du)--(8\du,34\du)--(7\du,36\du)--(10\du,38\du)--(10\du,40\du);
\draw[thick](5\du,0\du)--(5\du,1\du)--(5\du,2\du)--(3\du,5\du)--(3\du,6\du)--(2\du,7\du)--(3\du,8\du)--(2\du,10\du)--(1\du,11\du)--(2\du,12\du)--(1\du,13\du)--(1\du,14\du)--(0\du,15\du);
\draw[thick](10\du,0\du)--(10\du,1\du)--(8\du,4\du)--(7\du,5\du)--(8\du,6\du)--(8\du,7\du)--(7\du,8\du)--(7\du,10\du)--(6\du,13\du)--(5\du,14\du)--(5\du,15\du);
\draw[thick](0\du,15\du)--(-2\du,18\du)--(-5\du,19\du)--(-5\du,20\du)--(-7\du,21\du)--(-6\du,22\du)--(-8\du,23\du)--(-9\du,24\du)--(-10\du,25\du)--(-12\du,26\du)--(-12\du,27\du)--(-14\du,28\du)--(-15\du,29\du)--(-15\du,30\du);
\draw[thick](-15\du,30\du)--(-17\du,35\du)--(-16\du,40\du)--(-14\du,45\du)--(-15\du,50\du);
\draw[thick](5\du,15\du)--(5\du,17\du)--(5\du,19\du)--(7\du,21\du)--(6\du,23\du)--(6\du,25\du)--(7\du,27\du)--(7\du,29\du)--(8\du,31\du)--(8\du,33\du)--(10\du,35\du)--(10\du,37\du)--(10\du,40\du);
\draw[thick](-45\du,0\du)--(-44\du,1\du)--(-44\du,2\du)--(-43\du,3\du)--(-42\du,4\du)--(-41\du,5\du)--(-41\du,6\du)--(-40\du,7\du)--(-39\du,8\du)--(-40\du,9\du)--(-39\du,10\du);
\draw[thick](-50\du,0\du)--(-49\du,1\du)--(-48\du,2\du)--(-45\du,3\du)--(-44\du,4\du)--(-45\du,5\du)--(-44\du,6\du)--(-41\du,7\du)--(-40\du,8\du)--(-39\du,9\du)--(-39\du,10\du);
\draw[thick,->](-45\du,30\du)--(-36\du,25\du);
\node at (-45\du,30\du)[above]{\footnotesize species network};
\draw[thick,->](15\du,55\du)--(6\du,45\du);
\node at (15\du,55\du)[right]{\footnotesize gene genealogies};
\draw[thick,->](20\du,50\du)--(11\du,41\du);
\node at (20\du,50\du)[right]{\footnotesize multiple merger};
\draw[thick,->](-30\du,55\du)--(-17\du,51\du);
\draw[thick,->](-30\du,55\du)--(-7\du,60\du);
\node at (-30\du,55\du)[left]{\footnotesize binary mergers};
% \node at (-45\du,55\du)[below]{\footnotesize (or Kingman coalescent)};
% \node at (-30\du,55\du)[left]{\footnotesize multiple merger};
% \node at (-45\du,55\du)[below]{\footnotesize (or Kingman coalescent)};
\draw[thick,->](-50\du,15\du)--(-41\du,11\du);
\node at (-55\du,15\du)[above]{\footnotesize multiple merger};
\end{tikzpicture}